1. Field of the Invention
The present invention relates generally to designing and manufacturing contact lens eyewear and more specifically to a method for fitting contact lenses from high resolution imaging.
2. Description of the Related Art
Some patients require contact lenses shaped such that the edge of the contact lens rests on the sclera of the eye. The sclera is the whitish fibrous membrane (known as albuginea) that with the cornea forms the outer covering of the eyeball. Contact lenses having an edge that rests on the sclera are called corneascleral lenses or scleral lenses. However, historically, scleral contact lenses are difficult to fit. Patients that need scleral contact lenses often have irregularly-shaped eyes, making the fitting of a contact lens a time consuming and expensive process.
Past methods of fitting different kinds of contact lenses include keratometric measurements to measure the eye, empirical methods using trial lenses, or corneal videokeratography (topography). While these methods may be sufficient for simple lens designs, distinct disadvantages are inherent with more complex lenses, such as scleral or corneascleral lenses. These current methods are unable to measure accurately out to the scleral region of the eye.
For example, keratometric measurements reflect only the central three millimeters of the cornea. Thus, keratometric measurements produce insufficient data for producing scleral contact lenses. In another example, videokeratography relies upon derivation of the corneal shape from a series of rings projected onto the eye. However both this method and keratometric measurements are only approximations of the true shape of the cornea. Furthermore, neither method measures outside of the cornea onto the sclera.
Therefore, the area beyond the cornea must be estimated based on trial lens fittings using lenses of known curvatures and sizes using a method of bracketing the fit. The method of fitting using trial lenses is a long and laborious process, and can be very expensive if the lenses are difficult to manufacture, as is the case with scleral lenses. Additionally, arriving at a precise fit can require many weeks or months using many different trial lenses. During this time the patient is deprived of the desired or needed contact lens.